1. Field of the Invention
This invention relates to a sewing machine in which a sewing thread can automatically be released from a thread loop formed when a sewing needle is threaded, a threading control program and a recording medium on which the threading control program is recorded.
2. Description of the Related Art
There have conventionally been proposed sewing machines provided with threading means for automatically threading a sewing needle. For example, JP-8-173676-A discloses a technique for catching a thread by a hook having been-passed through an eye of the needle and returning the hook through the needle eye such that the needle thread is passed through the needle eye, while the thread is guided by thread guide grooves or the like and held by thread holders. JP-6-254279-A discloses thread drawing means for wiping a leading end of the cut thread off the cloth after a thread cutting operation such as in completion of sewing and introducing the thread end to an upper thread nipper.
In the sewing machine disclosed in JP-8-173676-A, however, the thread having been passed through the needle eye forms a loop between the needle eye and the hook. The thread loop is drawn with fingers of an operator so that a free end side part of the thread is pulled back through the needle eye, whereby the needle is threaded. JP-51-24353-A discloses a first nipper holding a thread cut during the sewing and a second nipper catching the thread held by the first nipper. The thread caught by the second nipper is passed through the needle eye by a thread extruder. The thread having been passed through the needle eye is caught by a third nipper, which is then moved upward so that the thread is completely passed through the needle eye. In the disclosed sewing machine, however, three nippers are provided for catching and pulling back the thread through the needle eye. Moreover, since the three nippers are moved individually, the structure of the sewing machine is complicated.